Avoid Screen Outs with SIGMA³ Engineering Workflows
Operators cite fracturing/stimulation and horizontal drilling as having the greatest impact on their spending plans. Between 2013 and 2014, the number of frac stages performed in the US went up almost 20% to 550,000. The roughly $38 Billion invested in frac services last year was tempered by failure rates (non-productive clusters/stages) as high as 40%. This is a very expensive problem, and especially painful in today's low-commodity environment.
Despite technology improvements, screen outs are just one of the factors contributing to number of under-performing frac stages. The industry average for screen outs is about 5%, amounting to a loss of approximately $2.7 Billion in lost frac services. The good news is that SIGMA³ averages a 99.3% success rate in horizontal screen out avoidance, and saved clients $22.7 Million just last year.
Screen Outs Have Tangible & Intangible Risks
Unless you are working in an extremely high-permeability environment where designing for a "tip screen out" is important to production, it's usually considered inefficient to screen out or "sand out" a frac stage.
Obviously, most shale operators in the US are not dealing with soft rock, but are stimulating unconventional wells with nano-permeability. Adding insult to injury, most of these wells are horizontal laterals with higher associated screen-out risk.
Screening out a conventional vertical well has some negative associated implications, but is somewhat mitigated by the fact that there might be sufficient "rat hole" to absorb this operational inefficiency. In the worst case, the operator can go into the well with appropriate tubing to facilitate the ultimate completion and thus circulate out the proppant from the wellbore with sufficient fluid viscosity and rate.
However, screening out horizontal laterals has both tangible, and intangible negative effects.
- Elevated risk of unsuccessfully executing subsequent stages on the lateral
- In a plug-and-perf completion, all proppant must be removed from the lateral wellbore or you at risk of "sticking" the next wireline perforating run.
- Estimated cost of up to $100K per screen-out, including coiled tubing cleanout, standby charges and sand/flowback disposal.
- Lost reserves via reduced far-field fracture dimensions and associated restricted conductivity.
- Dehydrated gel caused when excess sand is forced into the fractures of hard rock, but cannot deform, resulting in bridged proppant.
- Laboratory tests indicate that gel can be concentrated to values as high as 400 lbs/1000 gal equivalent.
- When gel is dehydrated, breakers that are in solution are rendered ineffective and the proppant pack becomes plugged up and nonconductive.
- Additionally, if enough pressure is applied to the dehydrated slurry, proppant crushing can occur due to point-to-point contact of the proppant grains, resulting in even further conductivity damage.
- "Stress shadowing" can influence the subsequent stage's net pressures, making proppant placement more challenging.
- The human factor, where engineers become understandably anxious after a screen out, resulting in more conservative sand scheduling on remaining the remaining stages. This isn't optimal in terms of production for neither the well nor the reservoir.
SIGMA³ On-Site Engineering Workflows Improve Outcomes
By precisely modelling the wellbore, frac fluids and proppant, our engineers are able to microanalyze the bottomhole net pressure response. We can spot trends, pressure inflections and proppant-bridging characteristics before they're evident in the surface pressure. This capability complements our information and experience sharing processes, which capture and retain learnings and observations from prior frac jobs in offset wells. In combining these capabilities, SIGMA³ consultants are best situated to predict what is most likely to happen as a frac job gets pumped, and when necessary, take decisive action when a screen out is imminent.
In today's world of extended lateral multi-stage frac projects, the completions engineer and qualified independent on-site frac consultant are as essential as a service company. After saving $22.7 Million last year, our clients tell us that their stimulations results improve when we're all working on the same team. With SIGMA³ on location and our extensive knowledge of hydraulic fracturing, we communicate directly with the Completions Engineers to design, execute, troubleshoot and optimize each stimulation.
Imagine the industry savings if SIGMA³ Engineering workflows were applied to just 10% of 550,000 frac stages. Imagine the savings if you applied them to yours?